Isolation of Cardiac and Vascular Smooth Muscle Cells from Adult, Juvenile, Larval and Embryonic Zebrafish for Electrophysiological Studies

Summary

The present protocol describes the acute isolation of viable cardiac and vascular smooth muscle cells from adult, juvenile, larval, and embryonic zebrafish (Danio rerio), suitable for electrophysiological studies.

Abstract

Zebrafish have long been used as a model vertebrate organism in cardiovascular research. The technical difficulties of isolating individual cells from the zebrafish cardiovascular tissues have been limiting in studying their electrophysiological properties. Previous methods have been described for dissection of zebrafish hearts and isolation of ventricular cardiac myocytes. However, the isolation of zebrafish atrial and vascular myocytes for electrophysiological characterization was not detailed. This work describes new and modified enzymatic protocols that routinely provide isolated juvenile and adult zebrafish ventricular and atrial cardiomyocytes, as well as vascular smooth muscle (VSM) cells from the bulbous arteriosus, suitable for patch-clamp experiments. There has been no literary evidence of electrophysiological studies on zebrafish cardiovascular tissues isolated at embryonic and larval stages of development. Partial dissociation techniques that allow patch-clamp experiments on individual cells from larval and embryonic hearts are demonstrated.

Introduction

Zebrafish are small teleost fish that have long been used as a model vertebrate organism¹ and have recently come to prominence as a viable vertebrate system for high throughput screening of genes and drugs^2,3. However, physiological analysis of zebrafish tissues is not well developed. In the cardiovascular system, methods have been described for dissection of zebrafish hearts⁴ and isolation of ventricular cardiac myocytes^5,6,7. There are few detailed descriptions of the effective isolation of atrial myocytes and no reports of vascular smooth muscle (VSM) preparations for patch-clamp studies.

The current work describes methodology for the isolation of zebrafish cardiac and vascular myocytes, viable for electrophysiological and functional studies. This approach includes modifications of previously reported protocols for zebrafish ventricular myocyte isolation^5,6 and adapts methods from mammalian VSM cell isolations⁸, allowing for the isolation of zebrafish vascular smooth muscle cells from the bulbous arteriosus (BA). The protocols result in efficient yields of isolated atrial, ventricular, and VSM cells from zebrafish that can be reliably used in patch-clamp studies for up to 8 h⁹.

Despite their nearly transparent larvae that develop entirely outside the parental organism, exploring their promised ontogenetic potential in studying cardiovascular development has been limited by challenges in extracting and analyzing tissues at a young age. The current article addresses this limitation by demonstrating patch-clamp experiments on zebrafish hearts isolated as early as 3 days post-fertilization (dpf), using an adapted, published extraction method¹⁰.

Protocol

All zebrafish (wild type strain AB, both male and female) were raised, maintained, and handled for the experiments following the guidelines of the Washington University Institutional Animal Care and Use Committee (IACUC). 1. Isolation of atrium, ventricle, and bulbous arteriosus from adult, juvenile, and larval zebrafish Euthanize fish using cold-shock, i.e., by immersing in 4 °C water, for ~10 s. Using curved forceps, transfer fish into a large Petr…

Representative Results

The above protocols reliably and routinely provide sufficient cardiac and vascular myocytes of consistent quality amenable for patch-clamp studies as recently reported in extensive studies of ATP-sensitive potassium (KATP) channels in wild-type and mutant zebrafish cardiovasculature9. Representative traces of recordings of such KATP channel activity from isolated cardiomyocytes are shown in Figure 3A-C. In the case of cells isola…

Discussion

Previous methods for isolating zebrafish ventricular myocytes^5,6, aimed at generating myocytes for culture or electrophysiological studies, provided cells of lower yield and involved lengthy steps of multiple centrifugations that adversely affected the cell quality and viability. The protocols described here are reliable, cover each of the significant cardiovascular tissues (ventricle, atria, and VSM), and importantly are quite practical for acute isolation of li…

Materials

1.5 mL Centrifuge Tubes	Eppendorf	22364111
10 mL Syringe	Fisher Scientific	14-955-459
19 Guage Needle	BD	305187
2,3-Butanedione Monoxime (BDM)	Sigma-Aldrich	B0753
5 mL Centrifuge Tubes	Sigma-Aldrich	EP0030119479	For embryonic heart isolation
Axopatch 200B amplifier and Digidata 1200 digitizer	Molecular Devices		Used for action potential recordings
Benchtop Mini Centrifuge	Southern Labware	MLX-106
Blebbistatin	Sigma-Aldrich	203390
Bovine Serum Albumin (BSA)	Sigma-Aldrich	A9418
Calcium Chloride	Sigma-Aldrich	C4901
Cell-Strainer Sieve	Cole-Parmer	EW-06336-71	100 μm sieve for embryonic heart isolation
Collagenase Type H	Sigma-Aldrich	C8051
Collagenase Type II	Worthington	LS004176
Collagenase Type IV	Worthington	LS004188
Curved Forceps	Fisher Scientific	16-100-110
DTT	Sigma-Aldrich	D0632
EGTA	Sigma-Aldrich	324626
Elastase	Worthington	LS003118
Fetal Bovine Serum (FBS)	Sigma-Aldrich	F2442
Fine Forceps	Dumont	Style #5	Ceramic-coated forceps for adult and juvenile CV tissue isolation (Need two)
Glucose	Sigma-Aldrich	G8270
HEPES	Sigma-Aldrich	H3375
Insulin	Sigma-Aldrich	I2643
K2ATP	Sigma-Aldrich	A8937
Large Petri Dish	Sigma-Aldrich	P5981	For dissociation
Magnesium Chloride	Sigma-Aldrich	M8266
Micro-Hematocrit Capillary Tubes	Kimble Chase	41A2502	Soda lime glass for patch pipettes
Papain	Worthington	LS003118
Pasteur Pipettes	Fisher Scientific	13-678-6A
Petri Dish	Sigma-Aldrich	P5606	100 mm x 20 mm, for embryonic heart isolation
Phosphate-Buffered Saline (PBS)	Sigma-Aldrich	806552
Potassium Chloride	Sigma-Aldrich	P3911
Scissors	Fine Science Tools	14090-09	For adult and juvenile zebrafish decapitation
Sodium Chloride	Sigma-Aldrich	S9888
Sodium Hydroxide	Sigma-Aldrich	S8045
Super Fine Forceps	Dumont	Style #SF	For isolating larval CV tissues (Need two)
Taurine	Sigma-Aldrich	T0625
Thermoshaker	ThermoFisher Scientific	13687711
Tricaine Methanesulfonate (MS222)			For anaesthetizing zebrafish larvae
Trypsin Inhibitor	Sigma-Aldrich	T6522